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USMLE Step 2 Quiz

USMLE Step 2 Quiz: Icu Monitoring Nutrition And Multisystem Failure

Practice Icu Monitoring Nutrition And Multisystem Failure in USMLE Step 2 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

Question 1 / 20

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A 25-year-old man is brought to the emergency department after being trapped under a collapsed structure for several hours. He has extensive crush injuries to his lower extremities. In the ICU, he is noted to have dark, tea-colored urine. His creatinine is 4.1 mg/dL, and his potassium is 6.5 mEq/L. He is receiving aggressive intravenous fluid resuscitation, but his urine output remains less than 20 mL/hr.

Which of the following is the primary indication for initiating urgent hemodialysis in this patient?

Select an answer to continue

What this quiz covers

This quiz focuses on Icu Monitoring Nutrition And Multisystem Failure, giving you a quick way to practice the rules, question types, and explanations that matter most for USMLE Step 2.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A 25-year-old man is brought to the emergency department after being trapped under a collapsed structure for several hours. He has extensive crush injuries to his lower extremities. In the ICU, he is noted to have dark, tea-colored urine. His creatinine is 4.1 mg/dL, and his potassium is 6.5 mEq/L. He is receiving aggressive intravenous fluid resuscitation, but his urine output remains less than 20 mL/hr.

Which of the following is the primary indication for initiating urgent hemodialysis in this patient?

  1. Creatinine > 4.0 mg/dL
  2. Oliguria refractory to fluid resuscitation
  3. Life-threatening hyperkalemia (correct answer)
  4. Myoglobinuria

Explanation: This patient has rhabdomyolysis causing acute kidney injury (AKI). While all the listed findings are concerning, the most urgent, life-threatening indication for hemodialysis is severe hyperkalemia (K > 6.5 mEq/L) that is refractory to medical management (e.g., calcium gluconate, insulin/glucose, beta-agonists). Hyperkalemia can cause fatal cardiac arrhythmias. High creatinine, oliguria, and myoglobinuria are all part of the AKI syndrome, but they do not carry the same immediate mortality risk as severe hyperkalemia. Therefore, managing the life-threatening electrolyte disturbance is the primary indication for dialysis.

Question 2

A 68-year-old man is in the intensive care unit (ICU) for septic shock secondary to pneumonia. He is intubated and mechanically ventilated. He is receiving intravenous norepinephrine to maintain a mean arterial pressure (MAP) of 65 mm Hg. A central venous catheter is in place, and his central venous pressure (CVP) is measured at 3 mm Hg (normal 8-12 mm Hg). His urine output has been 15 mL/hr for the past two hours. His heart rate is 125/min, and his extremities are cool.

Which of the following is the most appropriate next step in the management of this patient's hemodynamic instability?

  1. Administer an intravenous fluid bolus (correct answer)
  2. Increase the norepinephrine infusion rate
  3. Administer a dose of furosemide
  4. Initiate continuous renal replacement therapy

Explanation: This patient is in septic shock, a form of distributive shock characterized by vasodilation and capillary leak, leading to relative hypovolemia. His low central venous pressure (CVP) of 3 mm Hg, tachycardia, cool extremities, and low urine output all indicate inadequate preload despite vasopressor support. The most appropriate next step is to administer an intravenous fluid bolus to increase intravascular volume, improve preload, and enhance cardiac output. Increasing norepinephrine would address vasodilation but would not correct the underlying volume deficit. Furosemide is contraindicated as it would worsen hypovolemia. Renal replacement therapy is not indicated for initial hemodynamic management and is reserved for specific complications of acute kidney injury.

Question 3

A 55-year-old man with a history of alcohol use disorder is admitted to the hospital with severe acute pancreatitis. Over the next 48 hours in the ICU, despite aggressive fluid resuscitation, he develops worsening hypoxemia requiring mechanical ventilation. His blood pressure becomes labile, requiring vasopressor support. Laboratory studies show a creatinine that has increased from 1.0 mg/dL on admission to 2.8 mg/dL and a platelet count that has dropped from 250,000/mm³ to 80,000/mm³.

The development of these new clinical and laboratory findings is most indicative of which of the following processes?

  1. Hemorrhagic pancreatitis
  2. Disseminated intravascular coagulation
  3. Multiorgan dysfunction syndrome (MODS) (correct answer)
  4. Hepatorenal syndrome

Explanation: This patient's clinical course demonstrates the progressive failure of multiple organ systems following an initial insult (pancreatitis). He has developed respiratory failure (ARDS requiring ventilation), cardiovascular failure (hypotension requiring vasopressors), renal failure (acute kidney injury with rising creatinine), and hematologic dysfunction (thrombocytopenia). This clinical picture is the hallmark of multiorgan dysfunction syndrome (MODS), a common and life-threatening complication of severe systemic inflammation (SIRS) from conditions like pancreatitis or sepsis. While DIC and hepatorenal syndrome can be components of MODS, MODS is the best overarching diagnosis describing the failure of multiple distinct organ systems.

Question 4

A 62-year-old man with septic shock is being managed in the ICU. Despite 48 hours of appropriate antibiotics, fluid resuscitation, and vasopressor support, he remains anuric. His blood pressure is 90/50 mm Hg on norepinephrine. Laboratory results show: potassium 6.8 mEq/L, BUN 98 mg/dL, creatinine 5.4 mg/dL. An arterial blood gas shows pH 7.15, PaCO2 30 mm Hg, PaO2 85 mm Hg, and HCO3- 10 mEq/L.

Which of the following is the most compelling indication for initiating renal replacement therapy in this patient?

  1. Anuria
  2. Uremia (BUN > 90 mg/dL)
  3. Refractory metabolic acidosis (correct answer)
  4. Persistent hypotension

Explanation: The absolute indications for initiating urgent renal replacement therapy (RRT) can be remembered by the mnemonic AEIOU: Acidosis (severe, refractory), Electrolyte abnormalities (severe, refractory hyperkalemia), Intoxication, Overload (refractory fluid overload), and Uremia (symptomatic, e.g., pericarditis, encephalopathy). This patient has severe metabolic acidosis (pH 7.15) that is refractory to medical management, which is a life-threatening condition and a clear indication for RRT. While he also has severe hyperkalemia, refractory acidosis is often considered the most urgent indication in this combined picture. Anuria and a high BUN are concerning but are not, in isolation, absolute indications for immediate dialysis without other life-threatening complications.

Question 5

A 34-year-old man is in the ICU after an emergency laparotomy for a perforated duodenal ulcer with diffuse peritonitis. He is hemodynamically unstable, requiring high-dose norepinephrine, and has a large, open abdominal wound managed with a negative pressure dressing. He is expected to require prolonged mechanical ventilation and ICU care.

What is the most appropriate initial approach to nutritional support for this patient?

  1. Enteral nutrition via nasogastric tube
  2. Enteral nutrition via post-pyloric feeding tube
  3. Total parenteral nutrition (TPN) via central line (correct answer)
  4. No nutritional support until hemodynamically stable for 72 hours

Explanation: This patient has several contraindications to enteral nutrition (EN). He is in shock requiring high-dose vasopressors, which shunts blood away from the gut and increases the risk of non-occlusive bowel ischemia if EN is initiated. Additionally, his recent major intra-abdominal surgery with an open abdomen makes enteral feeding high-risk. In such cases where EN is contraindicated, total parenteral nutrition (TPN) should be initiated, typically after 5-7 days if the contraindication persists. However, given the high-risk surgery and instability, initiating TPN is the most appropriate plan, even if delayed a few days. Attempting EN (A or B) would be unsafe. Withholding nutrition for an extended period (D) is not ideal in a patient who is already catabolic from critical illness and surgery.

Question 6

A 70-year-old man with a large anterior wall myocardial infarction develops acute heart failure and cardiogenic shock. A pulmonary artery catheter is placed for hemodynamic monitoring. The following values are obtained: Central venous pressure (CVP): 18 mm Hg (normal 2-6) Pulmonary artery pressure: 55/28 mm Hg (normal 15-30/4-12) Pulmonary capillary wedge pressure (PCWP): 25 mm Hg (normal 6-12) Cardiac index (CI): 1.6 L/min/m² (normal 2.5-4.0) Systemic vascular resistance (SVR): 1800 dynes/sec/cm⁻⁵ (normal 800-1200)

These hemodynamic findings are most consistent with left ventricular failure. Which of the following interventions is most indicated to improve this patient's cardiac output?

  1. Intravenous fluid bolus
  2. Initiation of an inotropic agent (correct answer)
  3. Administration of a vasopressor agent
  4. Increased positive end-expiratory pressure (PEEP)

Explanation: The hemodynamic profile shows high filling pressures (high CVP and PCWP) and a severely reduced cardiac index, which is classic for cardiogenic shock due to left ventricular failure. The high SVR is a compensatory response to the low cardiac output. The primary problem is poor contractility. An intravenous fluid bolus would worsen the pulmonary edema (high PCWP). A pure vasopressor (like phenylephrine) would increase afterload (SVR) further, which would decrease cardiac output. Increasing PEEP is a ventilator strategy and does not directly address cardiac contractility. The most appropriate intervention is to initiate an inotropic agent (e.g., dobutamine, milrinone) to increase myocardial contractility, thereby improving the cardiac index.

Question 7

A 65-year-old woman is in the ICU for 5 days with severe community-acquired pneumonia and septic shock. Initially, she required only modest vasopressor support. Over the past 48 hours, her clinical status has worsened. Her norepinephrine requirement has increased, her total bilirubin has risen from 0.8 mg/dL to 4.2 mg/dL, and her platelet count has decreased from 180,000/mm³ to 70,000/mm³. Her creatinine remains stable.

The changes in her laboratory values and vasopressor requirement are most concerning for which of the following?

  1. Progression of liver cirrhosis
  2. Development of heparin-induced thrombocytopenia
  3. An unrecognized source of infection
  4. Worsening sepsis-induced organ dysfunction (correct answer)

Explanation: This patient is demonstrating evidence of worsening organ dysfunction in the setting of sepsis. The increasing vasopressor need signifies worsening cardiovascular dysfunction. The rising bilirubin indicates new liver dysfunction (cholestasis of sepsis), and the falling platelet count indicates new hematologic dysfunction. These findings, often tracked using scoring systems like the Sequential Organ Failure Assessment (SOFA) score, point towards worsening sepsis-induced multiorgan dysfunction. While an unrecognized source of infection could be the cause, the immediate process described is the organ dysfunction itself. There is no information to suggest pre-existing cirrhosis or heparin exposure, making those choices less likely.

Question 8

A 78-year-old man with metastatic non-small cell lung cancer is in the ICU with respiratory failure and septic shock from a hospital-acquired pneumonia. He is on maximal ventilatory support and three vasopressors. He has developed anuric renal failure. His family, who are his surrogate decision-makers, insist that 'everything' be done to prolong his life. The critical care team believes that continued aggressive care is medically futile and will only prolong the dying process.

Which of the following is the most appropriate next step for the medical team to take?

  1. Unilaterally withdraw life-sustaining treatment as it is futile.
  2. Continue all current life-sustaining treatments indefinitely as requested by the family.
  3. Request a formal ethics committee consultation to mediate the conflict. (correct answer)
  4. Obtain a court order to override the family's wishes.

Explanation: When there is a significant conflict between the medical team's assessment of futility and the family's wishes for continued life-sustaining treatment, the appropriate next step is to seek assistance in resolving the conflict. An ethics committee consultation provides a structured, multidisciplinary forum to review the case, ensure clear communication, and mediate the disagreement to find a resolution that respects the patient's interests. Unilaterally withdrawing care is ethically and legally problematic. Continuing futile treatment indefinitely is also ethically challenging as it can cause harm and suffering. Obtaining a court order is a last resort and should only be considered after all other avenues, like an ethics consult, have been exhausted.

Question 9

A 72-year-old woman is in the ICU for septic shock secondary to a urinary tract infection. On day 4 of her admission, she is noted to have developed scleral icterus. Her liver function tests show a total bilirubin of 7.2 mg/dL, a direct bilirubin of 5.9 mg/dL, and an alkaline phosphatase of 350 U/L. AST and ALT are mildly elevated at 80 U/L and 95 U/L, respectively. A right upper quadrant ultrasound shows no biliary ductal dilation and a normal-appearing gallbladder.

What is the most likely cause of this patient's jaundice?

  1. Ischemic hepatitis
  2. Drug-induced liver injury
  3. Cholestasis of sepsis (correct answer)
  4. Obstructive choledocholithiasis

Explanation: This patient's presentation is characteristic of cholestasis of sepsis, a form of intrahepatic cholestasis that occurs in critically ill patients. It is a manifestation of liver dysfunction as part of multiorgan dysfunction syndrome. The laboratory pattern shows a predominantly conjugated hyperbilirubinemia with a significant elevation in alkaline phosphatase and only mild elevations in transaminases. The normal ultrasound ruling out biliary obstruction is key. Ischemic hepatitis ('shock liver') typically presents with a dramatic, acute rise in AST and ALT into the thousands, which is not seen here. While drug-induced injury is possible, cholestasis of sepsis is far more common in this clinical context.

Question 10

A 44-year-old man is admitted to the ICU with necrotizing pancreatitis and septic shock. On day 3, the nurse notes spontaneous oozing of blood from his IV catheter sites and the development of scattered petechiae over his trunk. A complete blood count shows a platelet count of 35,000/mm³. Coagulation studies show a prothrombin time of 22 seconds, an aPTT of 55 seconds, a fibrinogen level of 80 mg/dL, and elevated D-dimer.

These findings are most characteristic of which of the following complications?

  1. Thrombotic thrombocytopenic purpura (TTP)
  2. Vitamin K deficiency
  3. Disseminated intravascular coagulation (DIC) (correct answer)
  4. Heparin-induced thrombocytopenia (HIT)

Explanation: The clinical picture of bleeding from multiple sites, thrombocytopenia, prolonged coagulation times (PT and aPTT), low fibrinogen, and elevated fibrin degradation products (D-dimer) in a critically ill patient with sepsis is classic for disseminated intravascular coagulation (DIC). DIC is a consumptive coagulopathy triggered by systemic inflammation (like sepsis or pancreatitis), leading to widespread microvascular thrombosis and subsequent hemorrhage as clotting factors and platelets are depleted. Vitamin K deficiency would prolong PT more than aPTT and would not cause such profound thrombocytopenia or low fibrinogen. TTP and HIT are not associated with prolonged coagulation times or low fibrinogen.

Question 11

A 45-year-old woman is admitted to the ICU with acute respiratory distress syndrome (ARDS) secondary to pancreatitis. She is intubated and placed on mechanical ventilation. Her hemodynamic status is stabilized with intravenous fluids and a low-dose vasopressor. She has no history of malnutrition. On day 2 of her ICU stay, she remains sedated and ventilated.

Which of the following is the most appropriate next step regarding nutritional support for this patient?

  1. Initiate total parenteral nutrition (TPN) within 24 hours.
  2. Initiate enteral nutrition via a nasogastric tube within 24-48 hours. (correct answer)
  3. Keep the patient NPO for 7 days to promote gut rest.
  4. Place a percutaneous endoscopic gastrostomy (PEG) tube for long-term feeding.

Explanation: For critically ill patients who are unable to maintain volitional intake, early enteral nutrition (initiated within 24-48 hours) is recommended. Enteral nutrition helps maintain gut mucosal integrity, reduces bacterial translocation, and is associated with fewer infectious complications and lower cost compared to parenteral nutrition. TPN is reserved for cases where enteral feeding is contraindicated or not tolerated. Prolonged NPO status increases the risk of malnutrition and related complications. A PEG tube is an invasive procedure and not indicated for initial nutritional support in the acute phase of critical illness.

Question 12

A 59-year-old man with ARDS is on mechanical ventilation with a PEEP of 15 cm H₂O. He is hypotensive with a MAP of 55 mm Hg despite adequate fluid resuscitation and is oliguric. A central venous catheter is in place, and his CVP is 18 mm Hg. His heart rate is 110/min, and jugular venous distension is noted on exam.

The patient's hypotension and oliguria are most likely due to which of the following mechanisms?

  1. Left ventricular failure
  2. Intravascular volume depletion
  3. Reduced preload due to high intrathoracic pressure (correct answer)
  4. Sepsis-induced vasodilation

Explanation: High levels of positive end-expiratory pressure (PEEP) increase intrathoracic pressure, which can compress the vena cava and reduce venous return to the right side of the heart. This decrease in preload leads to reduced right ventricular output, which in turn reduces left ventricular filling and output, causing hypotension (a form of obstructive shock). The high CVP of 18 mm Hg reflects the high intrathoracic pressure and right-sided congestion, not hypervolemia. Volume depletion would cause a low CVP. Left ventricular failure would typically present with a high PCWP. While the patient may have an underlying inflammatory state, the specific combination of high PEEP, high CVP, and hypotension strongly points to a preload reduction mechanism.

Question 13

An 88-year-old woman with advanced Alzheimer's dementia, who is nonverbal and bedbound at a nursing home, is admitted to the ICU for septic shock. She is intubated and on multiple vasopressors. She has no living will or durable power of attorney for healthcare. Her daughter, who is her primary caregiver, is at the bedside and asks, "What are her chances, doctor? Is she going to get better?"

Which of the following is the most appropriate initial response to the daughter's question?

  1. "It's too early to say; we need to give the antibiotics more time to work."
  2. "Her prognosis is very poor, and it is unlikely she will survive this hospitalization."
  3. "I understand this is a very difficult time. Let's talk about what you know of your mother's wishes and what is important to her." (correct answer)
  4. "We are doing everything we can to save her life and will continue all aggressive treatments."

Explanation: In situations involving critically ill patients with poor prognoses and no clear advance directives, the initial step in a goals-of-care discussion should be to explore the patient's values and previously expressed wishes through the surrogate decision-maker. This patient-centered approach, framed with empathy, opens a dialogue about what constitutes an acceptable quality of life for the patient. While the prognosis is indeed poor (B), stating this bluntly without first establishing rapport and understanding the patient's values can be jarring and counterproductive. Deferring the conversation (A) is inappropriate, and simply stating that everything is being done (D) avoids the necessary and difficult conversation about the potential burdens and benefits of continued aggressive care.

Question 14

A 58-year-old man who underwent a small bowel resection for Crohn disease has been receiving total parenteral nutrition (TPN) for the past three weeks due to a prolonged ileus. He now presents with a fever of 39.0°C (102.2°F), right upper quadrant abdominal pain, and a white blood cell count of 16,000/mm³. Liver function tests show a cholestatic pattern with an elevated alkaline phosphatase and total bilirubin. An abdominal ultrasound shows a distended gallbladder with thickened walls and pericholecystic fluid, but no gallstones.

Which of the following is the most likely diagnosis?

  1. Ascending cholangitis
  2. Acalculous cholecystitis (correct answer)
  3. TPN-induced cholestasis
  4. Catheter-related bloodstream infection

Explanation: This patient's clinical presentation and imaging findings are classic for acalculous cholecystitis. This condition is an inflammatory disease of the gallbladder without evidence of gallstones, typically occurring in critically ill patients. Major risk factors include prolonged fasting, TPN, trauma, and major surgery. TPN leads to gallbladder stasis, which promotes inflammation. The presentation of fever, RUQ pain, leukocytosis, and ultrasound findings of gallbladder wall thickening and fluid without stones is diagnostic. While TPN can cause cholestasis and the central line is a risk for infection, the specific constellation of RUQ pain and localized gallbladder inflammation on ultrasound points directly to acalculous cholecystitis.

Question 15

A 75-year-old man with no advance directives is in the ICU, incapacitated after a severe stroke. His wife of 50 years believes he would not want to be kept alive on a ventilator and requests a transition to comfort care. The patient's 45-year-old son, who lives out of state, arrives and vehemently disagrees, demanding that all aggressive treatments continue. There is no durable power of attorney for healthcare.

According to the generally accepted legal hierarchy for surrogate decision-making, whose preference should be prioritized?

  1. The son, as the next of kin.
  2. The wife, as the patient's spouse. (correct answer)
  3. The decision must be made by an ethics committee.
  4. The physician should make the decision in the patient's best interest.

Explanation: In the absence of a designated healthcare proxy, most jurisdictions follow a specific hierarchy to identify a surrogate decision-maker. The patient's spouse is almost universally considered the primary surrogate, followed by adult children, parents, and then other relatives. Therefore, the wife's decision should be given legal priority over the son's. While the physician's role is to facilitate communication and try to resolve the conflict, and an ethics committee may be helpful in mediating, the legal authority to make decisions rests with the spouse in this scenario. The physician makes the final decision only if no surrogate can be identified.

Question 16

A 40-year-old man sustained a devastating anoxic brain injury after a cardiac arrest. After 72 hours of observation in the ICU, a formal brain death evaluation is performed. The patient has no pupillary, corneal, oculocephalic, or gag reflexes. An apnea test is performed and is positive (no spontaneous respirations despite a PaCO2 > 60 mm Hg). A confirmatory EEG shows electrocerebral silence. The physician informs the family that the patient has died. The family states, "We are people of faith and we believe he can still recover. We do not want you to stop the ventilator."

Which of the following is the most appropriate next step?

  1. Continue mechanical ventilation as requested by the family.
  2. Arrange for a palliative care consultation to discuss hospice.
  3. Provide emotional support and allow the family a short time to grieve before discontinuing mechanical ventilation. (correct answer)
  4. Request an ethics committee meeting to decide on withdrawal of support.

Explanation: In the United States, brain death is legally and medically equivalent to cardiopulmonary death. Once a patient is declared brain dead, they are legally deceased. There is no ethical or legal obligation to continue physiologic support on a deceased person. The most appropriate and compassionate approach is to clearly explain to the family that the patient has died, provide strong emotional and spiritual support, and allow them a reasonable period to be with their loved one before discontinuing the ventilator. Continuing ventilation indefinitely is inappropriate as it treats a deceased person as if they were alive. Hospice is for living patients with terminal illness. An ethics meeting is not required to confirm the legal and medical reality of death.

Question 17

A 60-year-old woman in the ICU with severe acute pancreatitis has been NPO for 5 days. She is now hemodynamically stable and a decision is made to start enteral nutrition. A nasogastric tube is placed, but she has persistently high gastric residual volumes, suggesting gastroparesis. A nasojejunal (post-pyloric) feeding tube is successfully placed.

Which of the following is the most appropriate type of enteral formula to initiate in this patient?

  1. High-fat, calorie-dense formula
  2. Standard polymeric formula
  3. Semi-elemental or elemental formula (correct answer)
  4. High-fiber formula

Explanation: This patient has acute pancreatitis, a condition where pancreatic enzyme secretion is impaired. Standard polymeric formulas contain whole proteins, complex carbohydrates, and long-chain fats that require significant enzymatic digestion. Given the pancreatitis and need for post-pyloric feeding (bypassing the stomach to minimize pancreatic stimulation), a semi-elemental or elemental formula is most appropriate. These formulas contain nutrients in a pre-digested form (e.g., peptides or free amino acids, simple sugars, medium-chain triglycerides) that require minimal digestion and are more easily absorbed in the small intestine. A high-fat formula would excessively stimulate the pancreas, and a high-fiber formula is not indicated initially.

Question 18

A 67-year-old woman with ARDS has been receiving enteral nutrition via a nasogastric tube for the past week in the ICU. She is receiving 100% of her calculated caloric and protein needs. The medical team wants to confirm that the nutritional support is adequate for her metabolic demands.

Which of the following is the most reliable method for assessing the adequacy of protein provision in this critically ill patient?

  1. Measuring daily serum albumin levels
  2. Performing a 24-hour nitrogen balance study (correct answer)
  3. Monitoring daily body weight
  4. Measuring weekly serum prealbumin levels

Explanation: Nitrogen balance is a classic method used to assess the adequacy of protein provision. It is calculated as protein intake (in grams/6.25) minus urinary urea nitrogen (UUN) output plus an estimate for insensible losses. A positive nitrogen balance indicates an anabolic state, while a negative balance indicates a catabolic state where protein breakdown exceeds intake. In contrast, serum proteins like albumin and prealbumin are negative acute-phase reactants; their levels decrease due to inflammation in critical illness, making them unreliable markers of nutritional status. Daily body weight is heavily influenced by fluid shifts in the ICU and does not reflect nutritional adequacy.

Question 19

A 48-year-old homeless man with a history of chronic alcohol use is admitted to the ICU with community-acquired pneumonia and malnutrition. He is started on broad-spectrum antibiotics and enteral nutrition via a nasogastric tube. On the third day of hospitalization, he develops profound muscle weakness, confusion, and a cardiac monitor shows frequent premature ventricular contractions. An ECG is performed.

A deficiency of which of the following electrolytes is the most likely cause of this patient's clinical deterioration?

  1. Sodium
  2. Calcium
  3. Magnesium
  4. Phosphate (correct answer)

Explanation: This patient's presentation is classic for refeeding syndrome. He is severely malnourished (homeless, chronic alcohol use) and was started on nutritional support. The introduction of carbohydrates (in the enteral formula) stimulates insulin release, which causes a rapid intracellular shift of phosphate, potassium, and magnesium to be used in glycolysis and ATP production. Hypophosphatemia is the hallmark of refeeding syndrome and is responsible for the main clinical features: acute cardiopulmonary failure, rhabdomyolysis, seizures, and profound muscle weakness. While hypokalemia and hypomagnesemia also occur, severe hypophosphatemia is the primary driver of this syndrome's life-threatening complications.

Question 20

A 66-year-old man in the ICU for management of a COPD exacerbation has a radial arterial line for frequent blood gas monitoring. The nurse reports that the patient's right hand has become cool, pale, and the capillary refill is delayed compared to the left hand. The pulse oximeter waveform on the right index finger is dampened.

What is the most appropriate immediate action?

  1. Administer a bolus of intravenous heparin.
  2. Obtain an urgent vascular surgery consultation.
  3. Remove the arterial catheter. (correct answer)
  4. Elevate the hand above the level of the heart.

Explanation: The patient's signs and symptoms—a cool, pale hand with delayed capillary refill and a dampened waveform—are highly suggestive of acute limb ischemia secondary to thrombosis or embolism related to the radial arterial catheter. This is a medical emergency. The most appropriate and immediate action is to remove the catheter to eliminate the source of occlusion and potentially restore blood flow. While a vascular surgery consult and heparin may be needed, the first step is to remove the offending device. Elevating the hand would further decrease arterial perfusion and is contraindicated.